Refrigerator

ABSTRACT

By using a core made of laminated sheets of inorganic fibers having a particular shape and composition as part of a vacuum heat insulator for a heat insulation box, a heat insulation box excellent in long-term heat insulating properties and productivity can be provided. The vacuum heat insulator can be shaped easily. Therefore, a vacuum heat insulator suitable for a required heat insulation portion can be produced easily and applied to a heat insulation box. This property can increase coverage of the vacuum heat insulator on the heat insulation box, thus improving heat insulating properties of the heat insulation box. This can improve heat insulating properties and productivity of a refrigerator, thermal storage box, cold storage box, or vending machine, and contribute to energy savings.

FIELD OF THE INVENTION

The present invention relates to a heat insulation box that can be usedfor an apparatus, such as a refrigerator, thermal storage box, coldstorage box, vending machine, or water heater. It also relates to avacuum heat insulator used for these apparatus and to structure of thevacuum heat insulator.

BACKGROUND OF THE INVENTION

Energy saving in electric appliances is an unavoidable important problemthat has been addressed in recent years. Also, in a heat insulation boxused for a refrigerator and other various kinds of electric appliances,improvement in performance of a heat insulator is becoming essential. Onthe other hand, positive efforts to conserve terrestrial environment isbecoming important. One of urgent requests with regard to electricappliances is energy saving; thus, improving heat insulating propertiesof heat-related electric apparatus is becoming an important problem toaddress.

One heat insulator that has been recently developed, mainly bymanufacturers of electric appliances and heat insulators for energy andspace saving, is a vacuum heat insulator that has excellent heatinsulating properties. An example of the vacuum heat insulator is madeby covering a core, made of a rigid urethane foam having continuouspores with a gas-barrier laminated film, and evacuating an insidethereof. This vacuum heat insulator has heat insulating properties thatare approximately 2.5 times heat insulating properties of conventionalrigid or soft urethane foam or resin foam.

Japanese Patent Examined Publication No. H05-63715 discloses a vacuumheat insulator using a fibrous aggregate. A use of a fibrous aggregateof glass fibers, ceramic fibers, or resin fibers as a core of a vacuumheat insulator provides a light and deformable vacuum heat insulator.

Moreover, according to Japanese Patent Examined Publication No. 30-3139,a vacuum heat insulator made of a core of glass fibers, each having adiameter of 250 μm or smaller, is proposed. Inside of the vacuum heatinsulator is maintained to a degree of vacuum of 0.75 Pa or lower.Japanese Patent Laid-Open Publication No. 60-208226 discloses randomlylaminated inorganic fibers, having a small diameter, in a directionperpendicular to a heat transfer direction, and other fibers are sewnperpendicularly halfway to the laminated inorganic fibers to form a coreof a vacuum heat insulator.

An example of binding fibers using a binder is disclosed in JapanesePatent Laid-Open Publication No. H09-138058. In this invention, a fibermaterial such as glass wool is molded using an organic binder, and usedas a core of a vacuum heat insulator.

However, these conventional techniques have following problems and thusare difficult to be put to practical use.

For example, the vacuum heat insulator disclosed in Japanese PatentExamined Publication No. 30-3139 is difficult to be formed into aspecific shape because it is made of glass fibers only. When asheet-form vacuum heat insulator is to be produced, using glass fibersas a core of the vacuum heat insulator requires much manpower becausethe fibers themselves do not have shape-keeping properties.

Since inorganic fibers are sewn with other fibers in Japanese PatentLaid-Open Publication No. 60-208226, shape-keeping properties areimparted to the fibers themselves, and the problem with regard toshape-keeping properties is solved. However, as general methods cannotbe used to sew the fibers, while reducing heat conduction, this processhas a problem of high production costs.

Japanese Patent Laid-Open Publication No. H09-138058 proposes bindingfibers together using an organic binder as a method of impartingshape-keeping properties to the fibers. However, this publication onlydiscloses a type of the binder and does not disclose an amount of thebinder or a composition of the fibers. Thus, there is a problem in thatit is difficult to bind fibers together using the binder whilemaintaining heat insulating properties suitable for a vacuum heatinsulator. In addition, when organic fibers are used for a core, thecore generates gases during a long-term usage, and thus, heat insulatingproperties may be degraded.

In order to improve heat insulating properties of a heat insulation box,a heat insulation box that uses a heat insulator using a resin foam orpowder as the core has been proposed. Such a core has a problem oflong-term heat insulating properties or workability. As described above,conventional techniques have problems such as poor workability of thevacuum heat insulator, or a premature stage of product development, andadvantages of fiber aggregates are not utilized sufficiently.

In consideration of the above problems, the present invention aims toprovide a heat insulation box excellent in heat insulating propertiesand in productivity by using a vacuum heat insulator that includes acore made of laminated sheets of inorganic fibers. The core of thevacuum heat insulator is excellent in long-term reliability and inworkability.

SUMMARY OF THE INVENTION

In order to address the above problems, a heat insulation box of thepresent invention uses, as a heat insulator, a vacuum heat insulatorthat includes a core made of laminated sheets of an inorganic fibers,and a laminated film sandwiching the core. Further, a laminated filmdisposed on one side of the laminated sheets, and a laminated filmdisposed on another side of the laminated sheets, are different instructure from each other. Moreover, the vacuum heat insulator includesan adsorbent as required.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a vacuum heat insulator of the presentinvention.

FIG. 2 shows a cut-off portion provided along a side of inorganic fibersheets of a core of a vacuum heat insulator of the present invention.

FIG. 3 shows a cut-off portion provided in a part of an inorganic fibersheet as an uppermost sheet.

FIG. 4 shows a cut-off portion provided in a part of an inorganic fibersheet as an intermediate sheet.

FIG. 5 shows cut-off portions provided in parts of three inorganic fibersheets.

FIG. 6 is a perspective view of a refrigerator in accordance with asecond exemplary embodiment of the present invention.

FIG. 7 is a schematic view of a heat insulation box in accordance with athird exemplary embodiment of the present invention.

FIG. 8 is a schematic view of the heat insulation box in accordance withthe third exemplary embodiment of the present invention.

FIG. 9 is a schematic view of a heat insulation box in accordance with afourth exemplary embodiment of the present invention.

FIG. 10 is a schematic view of a heat insulation box in accordance withthe fourth exemplary embodiment of the present invention.

FIG. 11 is a schematic view of a lid in accordance with the fourthexemplary embodiment of the present invention.

FIG. 12 is a sectional view of a heat insulation box in accordance witha fifth exemplary embodiment of the present invention.

FIG. 13 is a sectional view of a refrigerator in accordance with a sixthexemplary embodiment of the present invention.

FIG. 14 is a sectional view of an insulation box in accordance with aseventh exemplary embodiment of the present invention.

FIG. 15 is a sectional view of a water heater in accordance with aneighth exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Exemplary embodiments of the present invention are described hereinafterusing specific examples.

First Embodiment

FIG. 1 is a sectional view of a vacuum heat insulator in accordance withan exemplary embodiment of the present invention. Vacuum heat insulator1 comprises core 2, enveloping member 3, and adsorbent 4.

One side of the enveloping member 3 is made of a four-layer laminatedfilm. An outermost layer of the laminated film is a polyamide layer (16μm in thickness) as a surface protection layer and an inner layer of thelaminated film is a polyethylene terephthalate layer (12 μm inthickness). Enveloping member 3 further has an aluminum foil (6 μm inthickness) as an intermediate layer, and a high-density polyethylenelayer (50 μm in thickness) for heat-sealing.

Another side of the enveloping member 3 is made of a four-layerlaminated film comprising surface protection layers of a polyamide layer(16 μm in thickness) and a polyethylene terephthalate layer (12 μm inthickness), an intermediate film layer made of an ethylene-vinyl alcoholcopolymer resin composite film (15 μm in thickness) having a vacuumdeposited aluminum on an inner side thereof, and a heat seal layer madeof a high-density polyethylene layer (50 μm in thickness).

In the vacuum heat insulator 1 of the present invention, a laminatedfilm of an aluminum foil is used for one side of the enveloping member3, and another side of the enveloping member is made of the laminatedfilm having the vacuum deposited aluminum. Thus, heat conduction isadjusted according to a temperature of an object that the vacuum heatinsulator contacts. As a result, the vacuum heat insulator in itsentirety can inhibit a heat leak caused by highly heat conductivealuminum foil, and an amount of gases entering into the vacuum heatinsulator can be suppressed because of an existence of the depositedaluminum film which is excellent in gas barrier properties.

In other words, because the aluminum foil is a metal film, it permits nogas entry even at elevated ambient temperatures. However, the resinlayers having thereon the vacuum deposited aluminum has permeabilitywith regard to gases in accordance with temperature increase.Gas-permeability decreases the degree of vacuum in the vacuum heatinsulator, thus deteriorating heat insulating properties of the vacuumheat insulator. To avoid this deterioration, it is effective to placethe aluminum foil side of enveloping member 3 of the vacuum heatinsulator on a side exposed to higher temperatures. Thus, the structureof the vacuum heat insulator of the present invention can suppressdegradation of performance caused by the heat leak and gas entry at thesame time.

However, the structure of the vacuum heat insulator of the presentinvention needs not to be limited to the above structure. On theassumption of cost reduction of the enveloping member and use of thevacuum heat insulator at high temperatures, crystalline polypropylene(50 μm in thickness) can be used as the heat seal layer in the abovestructure of enveloping member 3, for example. This structure canimprove a heat-resistant temperature of the vacuum heat insulator.

Alternatively, eliminating the polyamide layer as the outermost layerand slightly thickening the polyethylene terephthalate layer can reducecost due to elimination of the polyamide layer. In this case,degradation of bending resistance resulting from elimination of thepolyamide can be solved by a thickening of the polyethyleneterephthalate layer.

Moreover, depending on circumstances where the vacuum heat insulator isused, materials and structures of the enveloping member 3 should beselected. When the vacuum heat insulator is used at relatively lowtemperatures, such as in a refrigerator or cooler box, high-densitypolyethylene or the like is suitable as a material for the heat seallayer. When the vacuum heat insulator is used at relatively hightemperatures, such as in a water heater, a crystalline polypropylene,the ethylene vinyl alcohol copolymer resin, the polyethyleneterephthalate resin or a polyethylene naphthalate resin are suitable.

Alternatively, the enveloping member can be made of one kind oflaminated film without differentiating front and back sides of thevacuum heat insulator. In this case, sealing types of the envelopingmember 3 are not limited to a three-side seal. A so-called “gusset bag”or “pillow bag” can be used. The use of these bags can reduce a numberof protrusions along an outer periphery of enveloping member 3 resultingfrom heat-sealing, and further reduce a number of steps of folding theprotrusions.

Adsorbent 4 is placed in a cut-off portion provided in a part of core 2,except in uppermost and lowermost sheets thereof. This placement canaddress a problem of the adsorbent 4 protruding from the core 2 andbreaking enveloping member 3 during production of the vacuum heatinsulator.

As a material of adsorbent 4, the COMBO GETTER supplied by SEAS Gettersis excellent, which can absorb and remove moisture and carbon dioxide aswell as oxygen and nitrogen. Therefore, degradation of degree of vacuumof the vacuum heat insulator 1 can be inhibited for a long period oftime. Other examples of usable materials include a moisture adsorbent,such as calcium oxide and calcium chloride, and AGELESS (a registeredtrademark of Mitsubishi Gas Chemical Co., Inc). As a carbon dioxideadsorbent, any materials comprising calcium hydroxide can be used. Whenthese inorganic compounds are further combined with the above COMBOGETTER of the SEAS Getters, the effect as adsorbent is improved and theproperties of vacuum heat insulator 1 can be maintained for a longperiod of time.

Core 2 is laminated with four sheets of inorganic fiber 2 a. Cut-offportion 2 b is provided along a side of inorganic fiber 2 a. Adsorbent 4is disposed in the cut-off portion 2 b. This structure preventsadsorbent 4 from forming a protrusion on a surface of the vacuum heatinsulator. This structure makes fluid resistance of gases on a surfaceof the sheets different from that between the four laminated sheets at atime of evacuation of the vacuum heat insulator. As a result, vortexflow occurs in an air flow of sucked air, and the vortex flow improvesevacuation efficiency, thus remarkably improving productivity.

As another example of core 2, as shown in FIG. 3, recess 2 b can beformed in a first sheet of the inorganic fiber 2 a to house theadsorbent 4. Alternatively, as shown in FIG. 4, through hole 2 c can beformed through an intermediate sheet of inorganic fiber 2 a to house theadsorbent 4. Alternatively, as shown in FIG. 5, through holes 2 d can beformed through three of the sheets of the inorganic fiber 2 a to housethe adsorbent 4.

The number of sheets 2 a to be laminated is not specifically limited.However, in order to prevent adsorbent 4 from forming a protrusion, atleast three sheets are preferable. In consideration of improvement inproductivity, at least four sheets are more preferable.

In the present embodiment, the core 2 contains 50 to 65 wt. % of SiO₂,10 to 20 wt. % of Al₂O₃ and CaO each, and 1 to 4 wt. % of MgO, based onthe composition of the material of the core.

SiO₂ is used as a major constituent because this material has a low heatconductivity and is inexpensive . The content of SiO₂ suitable for thevacuum heat insulator 1 preferably ranges from 50 to 65 wt. % of thecomposition of the material of the core 2, and more preferably from 55to 60 wt. % thereof.

Al₂O₃ is added so as to improve a heat resistance of the core 2. Inconsideration of heat conductivity of Al₂O₃ itself, a small contentthereof is more preferable. When a balance of heat resistance and heatconductivity is considered, the recommendable amount of Al₂O₃ to beadded ranges from 10 to 20 wt. %. If an amount of Al₂O₃ of is less than10 wt. %, heat resistance is poor. If an amount exceeds 20 wt. %, heatinsulating properties of the vacuum heat insulator 1 tend to degrade.

On the other hand, CaO serves to adsorb moisture, and an added amount of10 to 20 wt. % of CaO provides excellent heat insulating properties.Even when the amount is increased to more than 20 wt. %, moistureadsorption is not so improved. If the amount is less than 10 wt. %,improvement of performance of the vacuum heat insulator 1 with regard tomoisture adsorption is not recognized.

Addition of MgO is effective in improving mutual cohesive forces of thefibers. Particularly when fiber sheets are produced by a wet paperforming method, addition of MgO is more effective. With addition of 1 to4 wt. % of MgO, improvement in cohesive forces is recognized, and withan amount exceeding 4 wt. %, there is no additional improvement. Whenthe added amount of MgO is reduced, the cohesive forces decreases.Therefore, addition of 1 to 4 wt. % of MgO is preferable.

The material composition of the fibers used for core 2 is described asabove. Because a diameter and a bulk density of the fibers alsoinfluence heat insulating properties of the vacuum heat insulator 1,optimum physical properties should be specified.

As for the fiber diameter of the core 2, 1 to 3 μm is preferable. For afiber diameter smaller than 1 μm, manpower in production of the fibersremarkably increases. Moreover, as special equipment for producingfibers is required, industrially economical production becomesdifficult. In addition, fibers are excessively entangled with each otherto form large fibrous aggregates and thus large pores are formed. Thisincreases gas heat conductivity based on gas heat conduction, thusdegrading heat insulating properties.

When the fiber diameter is larger than 3 μm, pores formed by aggregationof the fibers are large. For this reason, heat conduction by gasesexhibits a greater influence; thus, heat insulating properties degrade.In order to inhibit heat conduction by gases, a degree of vacuum ofapproximately 13 Pa, which allows efficient industrial production, isinsufficient, and a degree of vacuum of approximately 0.13 Pa isrequired. But, this degree of vacuum renders efficient industrialproduction difficult.

Therefore, in consideration of industrial productivity, a fiber diameterranging from 1 to 3 μm is suitable. A fiber diameter ranging 2 to 3 μmis more preferable.

On the other hand, even material having such a fiber diameter range mayadversely affect heat insulating properties of the vacuum heat insulatorif bulk density of the fibers is not appropriate. When bulk density ofthe fibers is higher than 0.3 g/cm³, solid heat conduction of the fibershas a greater influence, and heat insulating properties are degraded. Inaddition, such a high bulk density reduces flexibility of the vacuumheat insulator imparted by use of a fiber material, thus making thevacuum heat insulator unsuitable for an application to protruded andrecessed portions. Application to such portions is one of thecharacteristic features of the present invention.

When the bulk density of the fiber is lower than 0.1 g/cm³, theproportion of fibers in a given space reduces and air gaps increase.This results in an increase of gas heat conduction, thus degrading heatinsulating properties of the vacuum heat insulator. Another problem isthat atmospheric compression at a time of production of the vacuum heatinsulator increases the degree of deformation and makes it difficult toproduce a vacuum heat insulator of stable shape.

As a result, the bulk density of a fiber material suitable for thevacuum heat insulator preferably ranges from 0.1 to 0.3 g/cm³, and morepreferably from 0.1 to 0.2 g/cm³.

In order to form fibers into a sheet, it is desirable to bind the fibersusing a binder. However, an inappropriate type of binder or an amount ofbinder affects heat insulating properties of the vacuum heat insulator.

For example, using an inorganic material as a binder results in a highdensity of a sheet produced from the fibers and binder. Even withorganic binders, thermosetting resins, such as phenolic resin, causegasification of unreacted monomers in a vacuum atmosphere. Gasificationdegrades the degree of vacuum, thus adversely affecting heat insulatingproperties of the vacuum heat insulator.

On the other hand, when thermoplastic resins are used as a binder, theabove adverse effect caused by unreacted monomers can be reduced. Whensheets are produced by the wet paper forming method, a use ofwater-soluble polymers is preferable as a binder. From such a viewpoint,water-soluble acrylic resins are suitable. Being water-soluble polymers,the water-soluble acrylic resins can uniformly disperse on surface offibers, even when a sheet is produced by the wet paper forming method.Thus, a fibrous sheet having uniform bonding strength can be obtained.

Even when water-soluble acrylic resins are used as a binder, an amountto be added is an important factor. For an amount of less than 3 wt. %,a sheet of fibers can be formed but is broken when wound like a roll.Thus, stable production is difficult. For an amount exceeding 10 wt. %,viscosity of a slurry used in production of sheets by the wet paperforming method is high, thus deteriorating productivity.

For these reasons, the suitable amount of an acrylic binder to be addedranges from 3 to 5 wt. %. An amount from 3 to 4 wt. % is morepreferable.

However, when productivity of sheets of fibers can be neglected,excellent heat-insulating properties for a vacuum heat insulator can beobtained even without using a binder.

Hereinafter a specific method of producing the vacuum heat insulator 1of the present invention is described.

The core 2 of the above structure is dried in a drying oven at atemperature of 130° C. for one hour. Thereafter, enveloping member 3 isfilled with the core 2 together with adsorbent 4, evacuated, and thensealed to form vacuum heat insulator 1.

A heat conductivity of the vacuum heat insulator 1 obtained in thismanner ranges 0.0035 to 0.0038 W/mK at an average temperature of 24° C.It has proved that this value corresponds to approximately twice heatinsulating properties of a conventional vacuum heat insulator usingsilica power, and a vacuum heat insulator using an open-pored urethanefoam.

Second Embodiment

FIG. 6 is a perspective view of a refrigerator in accordance with asecond embodiment of the present invention. Refrigerator 5 of thepresent embodiment uses, as heat insulator 1, the vacuum heat insulatordescribed in the first embodiment. The refrigerator 5 has a freezercompartment 6 at a bottom and a machine room 7 at a back bottom portion.A refrigerant piping 8 is attached to outer box 9 with aluminum tapes. Arigid urethane foam (not shown) using cyclopentane as a foaming agent isfilled in a space between an inner box (not shown) and outer box 9. Onboth side faces of the freezer compartment 6 of the refrigerator 5,vacuum heat insulator 1 produced in accordance with the first embodimentis provided. Between the vacuum heat insulator 1 on the sidefaces of thefreezer compartment 6 and outer box 9, to which the vacuum heatinsulator is to be attached, the high-temperature refrigerant piping 8is provided. Moreover, the heat insulator 1 is shaped to substantiallycover the sidefaces of the freezer compartment 6. Furthermore, analuminum foil side of composite laminated film of the vacuum heatinsulator 1 is placed on a side exposed to the high-temperaturerefrigerant piping 8.

This structure allows efficient heat insulation of sidewalls of thefreezer compartment and inhibits entry of heat from the high-temperaturerefrigerant piping 8 into the freezer compartment 6, thus providing arefrigerator having low power consumption. Moreover, this structure canalso inhibit degradation of heat insulating properties caused byliquefaction and decrease of a urethane blowing agent that occurs whencooled to a temperature of −18° C.

In addition, the refrigerator 5 of the present invention also has thevacuum heat insulator 1 between machine room 7 and freezer compartment6. Temperature is highest in machine room 7 because a compressoroperates therein. Therefore, use of the vacuum heat insulator 1 betweenmachine room 7 and freezer compartment 6 is effective.

Having flexibility, the vacuum heat insulator 1 of the present inventioncan be applied along a stereoscopic shape of the machine room 7.Moreover, having high heat resistance, the vacuum heat insulator 1 canbe used for space between the machine room 7 and the freezer compartment6, and can be provided in a the machine room. Thus, a refrigeratorexcellent in energy saving and cost-performance can be provided.

Third Embodiment

FIG. 7 is a sectional view of a heat insulation box 101 in accordancewith a third embodiment of the present invention. The heat insulationbox 101 forming a refrigerator uses vacuum heat insulator 1 of the firstembodiment. The heat insulation box 101 comprises an inner box 102 of avacuum-molded ABS resin, an outer box 103 of a press-molded iron sheet,and a flange 104. To form the heat insulation box 101, the vacuum heatinsulator 1 is provided inside of the outer box 103 beforehand, and thenurethane resin is filled into a space between the inner box and outerbox and foamed so as to surround the vacuum heat insulator 1 with rigidurethane foam 106.

FIG. 8 is a schematic view of the heat insulation box 101. A top wall ofthe heat insulation box is provided with one sheet of the vacuum heatinsulator 1, as are a back wall and each of two side walls. According toa shape of the heat insulation box 101, the sheet of vacuum heatinsulator 1 used for each side wall is cut along one side to fit to ashape of the sidewall.

Fourth Embodiment

FIG. 9 is a schematic view of a heat insulation box in accordance withan example of the present embodiment.

Heat insulation box 108 is used as a cooler, and comprises a box 109 andlid 110.

FIG. 10 is a schematic view of a box in accordance with another exampleof the present embodiment.

Box 109 is integrally molded by adhering vacuum heat insulator 1 onto aninner surface of an outer box 112 using double-sided adhesive tape in aspace formed between the inner box 111 and the outer box 112 made ofpolypropylene, and thereafter filling the space between inner box 111and outer box 113 with urethane resin and then foaming the urethane asto surround the vacuum heat insulator with rigid urethane foam 106.

FIG. 11 is a schematic view of a lid in accordance with still anotherexample of the present embodiment.

Vacuum heat insulator 1 including adsorbent 4 is disposed in a foamedpolystyrene 113, and packed in a space formed between an inner frame 114and an outer frame 115.

With reference to FIG. 10, vacuum heat insulator 1 is made by bending asheet of vacuum heat insulator 1 into the C-shape to fit to a shape ofheat insulation box 109.

Having a sheet-form core, vacuum heat insulator 1 can be bent into theC-shape easily. This improves coverage of the vacuum heat insulator 1 onthe heat insulation box 109, thus improving heat insulating propertiesof the heat insulation box 109.

With reference to FIG. 11, lid 110 comprises a foamed polystyrene 113having a recess that has been formed corresponding to a shape of vacuumheat insulators, and the vacuum heat insulator is buried within therecess. The polystyrene is placed in a space formed between the innerframe 114 and the outer frame 115 made of polypropylene.

As the vacuum heat insulator 1 used for lid 110 is smaller than thevacuum heat insulator used for the box 109, a ratio of areas of sealingportions in enveloping member 3 increases in vacuum heat insulator 1.This is considered to give greater influence to gases entering from thesealing portions of the enveloping member over a long period time, andincreases an aged degradation of performance of the vacuum heatinsulator, and thus degrades heat insulating properties. For thisreason, adsorbent 4 is used with the vacuum heat insulator 1 for the lid110.

It is desirable to use an adsorbent 4 that is made of a room temperatureactivation type getter material for adsorbing and removing at leastnitrogen, oxygen, moisture, and carbon dioxide. Specific examplesinclude an oxygen adsorbent essentially consisting of iron powder, whichis commercially available under a trade name of AGELESS, for example.

Fifth Embodiment

FIG. 12 is a sectional view of a heat insulation box of the presentembodiment.

Heat insulation box 118 forming a refrigerator comprises an inner box119 of a vacuum-molded ABS resin, and an outer box 120 of a press-moldediron sheet. Vacuum heat insulator 1 is provided between the inner box119 and the outer box 120, and space between the inner box and outer boxis filled with urethane resin, which is foamed so as to surround thevacuum heat insulator with rigid urethane foam 121.

A thermoplastic resin 122 is applied to an inner surface of the outerbox 120 beforehand so as to fit to an outer periphery of core 2 and hasa width of 10 mm. Thermoplastic resin 122 is heat-sealed to the heatseal layer of enveloping member 3 of the vacuum heat insulator 1.Desirable thermoplastic resins include high-density polyethylene,low-density polyethylene, and polypropylene.

In the present embodiment, because a laminated sheets of an inorganicfiber that is light, excellent in surface planarity, and thin, is usedas the core 2, an adhesive property between the vacuum heat insulator 1and the inner surface of the outer box 120 is excellent. This improvesthe heat insulating properties. In addition by, being light and thin,the vacuum heat insulator 1 is not displaced by its own weight whenattached to the inner surface of the outer box 120. Furthermore, byhaving a thin core 2, the vacuum heat insulator 1 does not hinderfluidity of urethane resin when it is filled into the space between theinner box 119 and the outer box 120 and foamed. Thus, rigid urethanefoam can uniformly fill the space between the inner box 119 and theouter box 120 without forming any voids. Therefore, heat insulatingproperties of the entire heat insulation box 118 improves.

Sixth Embodiment

FIG. 13 is a sectional view of a refrigerator in accordance with anexemplary embodiment of the present invention.

Heat insulation box 201 comprises an inner box 202 of a vacuum-moldedABS resin and outer box 203 of a press-molded iron sheet, which areengaged with each other via a flange. Vacuum heat insulator 1 isprovided inside of the outer box 203 beforehand, and then urethane resinis filled into a space between the inner box 202 and the outer box 203and foamed so as to surround the vacuum insulation with rigid urethanefoam 204.

Heat insulation box 201 is horizontally divided by a partition 205 intoan upper part and a lower part. The upper part forms a refrigeratorcompartment and the lower part forms a freezer compartment. Twoevaporators 206 are provided. One is used for cooling the refrigeratorcompartment and the other is used for cooling the freezer compartment.

In addition, a compressor 208, a control circuit board 209, and acondenser 200 are disposed in a machine room 207 at a bottom of therefrigerator. The evaporator 206 for cooling the freezer compartment isdisposed outside of the machine room 207 and inside of the inner box202. The heat insulation box 201 is formed so as to house the evaporator206 in this manner.

Because the vacuum heat insulator 1 of the present invention hasexcellent heat insulating properties, even a thin sheet of the vacuumheat insulator can provide sufficient heat insulation, thus greatlycontributing to increasing volume of storage space in the refrigerator.Especially, even though the disposition of the two evaporators 206decreases a volume of the refrigerator compartment in the presentembodiment, use of a thin and excellent vacuum heat insulator 1 canlimit this decrease in volume.

Disposition of a plurality of sheets of vacuum heat insulator 1 on back,side, and top walls of the refrigerator can further increases volume ofstorage space in the refrigerator. However, disposition of a largenumber of vacuum heat insulators 1 may increase cost.

As for a method of disposing the vacuum heat insulator 1 of the presentembodiment, the vacuum heat insulator is attached to an inside of theouter box 203 with double-sided adhesive tape or the like, andthereafter the space between the inner box 202 and outer box 203 isfilled with urethane 204.

In addition, for the refrigerator of the present embodiment, the heatinsulating part in partition 205 is also integrally filled with rigidurethane foam 204. The vacuum heat insulator 1 is also disposed inpartition 205 to reduce a thickness of the partition. This contributesto increasing the volume of the storage space in the refrigerator.

In the present embodiment, the upper part of the heat insulation box 201divided by the partition 205 is a refrigerator compartment, and thelower part is a freezer compartment. The refrigerator compartment may befurther divided to also provide a crisper compartment, for example. Thefreezer compartment may be further divided to also provide an,ice-maker, and a partially freezing compartment.

Vacuum heat insulator 1 provided in a heat insulating part forseparating machine room 207 from the freezer compartment is bent andshaped to fit to a shape the machine room 207. Using a sheet-shape core,the vacuum heat insulator 1 can be bent easily with excellentproductivity. When a plurality of sheets of the vacuum heat insulatorare combined for insulation in a conventional manner, gaps betweensheets of the vacuum heat insulator cause degradation of heat insulatingproperties. In contrast, as shown in the present invention, use of asheet of a vacuum heat insulator that can be bent results in animprovement in heat insulating properties that leads to an energy savingby allowing for a shorter operating time of the compressor 208.

In the present embodiment, the freezer compartment, the compressor 208,the control circuit board 209, and condenser 200 are insulated by asingle vacuum heat insulator 1.

Therefore, a temperature increase in the freezer compartment caused byheat generated from the compressor, the control circuit board, and thecondenser can be inhibited. In the present embodiment, because each ofthe compressor and freezer compartment, the control circuit board andfreezer compartment, and the condenser and freezer compartment need notbe insulated separately, heat insulation can be performed veryefficiently.

In addition, because inorganic fibers are non-flammable, the vacuum heatinsulator has a non-flammable structure and is unlikely to generatetoxic gases. Therefore, the refrigerator using this vacuum heatinsulator is also non-flammable. For such a reason, the refrigerator isalso excellent in safety.

Furthermore, even when flammable substances such as carbon-hydride areused, for the refrigerator, as a foaming agent of the resin,refrigerant, or the like, the vacuum heat insulator has a non-flammablestructure because inorganic fibers are used. Thus, the refrigerator ofthe present embodiment can be a refrigerator excellent in safety.

Seventh Embodiment

FIG. 14 is a sectional view of heat insulation box 210 forming aninsulation box, in accordance with the seventh embodiment of the presentinvention.

Insulation box 210 comprises a body 211, a lid 212, an outer box 213, aninner box 214, a cold storage unit 215, a heat insulator 216, and avacuum heat insulator 1.

With regard to the insulation box 210, because vacuum heat insulator 1of the present invention has flexibility, it can integrally be attachedto an insulation box of a substantially cubic shape if it is bentbeforehand. Thus, because a number of joints of vacuum heat insulator 1can be reduced, heat leak from joints can be reduced.

Moreover, when protrusions and recesses for housing the cold storageunit 215 are formed in the lid 212, the vacuum heat insulator 1 can beattached to the protrusions and recesses because it has flexibility.Thus, heat insulation properties can be efficiently improved.

Because the insulation box 210 of the present embodiment cansufficiently use effects of the vacuum heat insulator 1, heat insulatingproperties, that the conventional insulation box could not provide, canbe obtained. Therefore, such an insulation box can be used as a medicalcold-box requiring stricter temperature control, as well as a leisurecooler.

Materials of the cold storage unit 215 are not specifically limited.Commercially available general cold storage agents can be used. Theinsulator 216 is not specifically limited as well. Examples of usableheat insulators include commercially available foamed resins such as arigid urethane foam and polystyrene foam, and fiber materials such asglass wool.

Vacuum heat insulator 1 can be attached to either one of the outer box213 and the inner box 214 in the body 211. In either case, the sameeffects can be obtained.

Eighth Embodiment

FIG. 15 is a sectional view of a water heater in accordance with anexemplary embodiment of the present invention. The water heater 317comprises a body 318, a hot water reservoir 319, a lid 320, a heater321, and vacuum heat insulators 1. The vacuum heat insulator 1 isattached so as to wind around an outside of the hot water reservoir 319.In addition, the vacuum heat insulator 1 is bent and extended to avicinity of the heater 321. Furthermore, another vacuum heat insulator 1is provided in a recess in the lid 320.

With a water heater 317 of such a structure, when inorganic fibermaterial having high heat resistance is used as core 2 of the vacuumheat insulator 1, the vacuum heat insulator 1 is unlikely to be degradedby heat. Thus, the vacuum heat insulator has no problem when the waterheater is used even for a long period of time. Moreover, by havingflexibility, the vacuum heat insulator 1 can be bent, extended to thevicinity of the heater, and used in the recess in the lid.

Because the vacuum heat insulator 1 has high heat resistance andflexibility, water heater 317 of the present embodiment can efficientlyreduce power consumption and realize downsizing.

INDUSTRIAL APPLICABILITY

As described above, the vacuum heat insulator of the present inventionuses laminated sheets of inorganic fibers as a core. The heat insulationbox of the present invention uses the vacuum heat insulator of thepresent invention. Therefore, because the vacuum heat insulatorgenerates very little gas through time and has excellent workability, aheat insulation box excellent in long-term reliability and productivitycan be obtained. In addition, use of a thin sheet-form material as thecore makes the heat insulation box thinner, thus contributing to a spacesaving of the heat insulation box.

Because the core used for this invention can be shaped easily,lamination and machining such as bending and formation of a cut-offportion, recess, or through hole, can be performed easily. Therefore, avacuum heat insulator suitable for a required heat insulation portioncan be produced easily and applied to a heat insulation box, such as arefrigerator. In other words, coverage of the vacuum heat insulator inthe heat insulation box increases and thus heat insulating properties ofthe heat insulation box also improves. In addition, the vacuum heatinsulator includes a thin sheet-form core. Therefore, when used for apartition in the heat insulation box, the vacuum heat insulator canprovide a thin partition, thus allowing efficient use of space in theheat insulation box.

For these reasons, use of the vacuum heat insulator of the presentinvention for equipment requiring heat insulation, such as arefrigerator, accomplish improvement in productivity and energy savingas well as downsizing of equipment.

1. A refrigerator comprising: a heat insulating box including an innerbox having an opening, an outer box, a lid for closing said opening, atleast one vacuum heat insulator disposed in a space between said innerbox and said outer box at at least one of a back wall, a side wall and atop wall of the refrigerator, said at least one vacuum heat insulatorcomprising a core disposed in an enveloping member, and foamed resinfilled in said space between said inner box and said outer box, saidfoamed resin employing a flammable substance as a foaming agent; and acooling machine for cooling an inner space of said heat insulating box,said cooling machine employing a flammable substance as a refrigerant,wherein said core is made of a fibrous laminate of at least two sheetsof inorganic fibers, with opposing faces of said sheets being in contactwith each other, said inorganic fibers containing SiO₂ as a maincomposition of said inorganic fibers, and further containing Al₂O₃, CaOand MgO as material compositions, and wherein said enveloping member ismade of a laminated film.
 2. The refrigerator according to claim 1,wherein said laminated film includes a first portion on a first side ofsaid core and a second portion on a second side of said core, with saidfirst portion and said second portion having different structuresrelative to one another.
 3. The refrigerator according to claim 1,further comprising an adsorbent in said at least one vacuum heatinsulator.
 4. The refrigerator according to claim 1, further comprisinga freezer compartment at a bottom thereof and a machine room outside ofsaid freezer compartment, wherein said at least one vacuum heatinsulator includes a vacuum heat insulator that covers sidewalls of saidfreezer compartment.
 5. The refrigerator according to claim 4, furthercomprising high-temperature refrigerant piping provided between said atleast one vacuum heat insulator and said outer box.
 6. The refrigeratoraccording to claim 4, wherein said at least one vacuum heat insulatorincludes a vacuum heat insulator that is provided between said machineroom and said freezer compartment.
 7. The refrigerator according toclaim 1, further comprising independent compartments having differenttemperature ranges, and an evaporator for each of said compartments,wherein said at least one vacuum heat insulator includes a vacuum heatinsulator that is disposed in a heat insulating portion behind at leastone of said evaporators.
 8. The refrigerator according to claim 7,wherein said at least one vacuum heat insulator includes a vacuum heatinsulator that is disposed in a partition between said independentcompartments.
 9. The refrigerator according to claim 1, furthercomprising a compressor, wherein said at least one heat insulatorincludes a vacuum heat insulator that is disposed in a partition betweensaid compressor and said inner box.
 10. The refrigerator according toclaim 1, further comprising a control circuit board, wherein said atleast one vacuum heat insulator includes a vacuum heat insulator that isdisposed in a partition between said control circuit board and saidinner box.
 11. The refrigerator according to claim 1, further comprisinga condenser in a bottom thereof, wherein said at least one vacuum heatinsulator includes a vacuum heat insulator that is disposed in apartition between said condenser and said inner box.
 12. Therefrigerator according to claim 1, further comprising a thermoplasticresin layer on at least a portion of an inner surface partially definingsaid space between said outer box and said inner box, wherein said atleast one vacuum heat insulator is adhered to said inner surface viasaid thermoplastic resin layer by performing a hot melt bondingoperation.
 13. The refrigerator according to claim 1, wherein said atleast one vacuum heat insulator includes plural vacuum heat insulators,with a first of said plural vacuum heat insulators positioned between aback wall of said inner box and a back wall of said outer box on anouter box side of said space, with a second of said plural vacuum heatinsulators positioned between a top wall of said inner box and a topwall of said outer box on the outer box side of said space, with a thirdof said plural vacuum heat insulators positioned between a first sidewall of said inner box and a first side wall of said outer box on theouter box side of said space, and with a fourth of said plural vacuumheat insulators positioned between a second side wall of said inner boxand a second side wall of said outer box on the outer box side of saidspace.
 14. The refrigerator according to claim 13, wherein saidlaminated film includes a first portion on a first side of said core anda second portion on a second side of said core, with said first portionand said second portion having different structures relative to oneanother.
 15. The refrigerator according to claim 13, further comprisingan adsorbent in each of said plural vacuum heat insulators.
 16. Therefrigerator according to claim 13, further comprising a freezercompartment at a bottom thereof and a machine room outside of saidfreezer compartment, wherein said at least one vacuum heat insulatorincludes a vacuum heat insulator that covers sidewalls of said freezercompartment.
 17. The refrigerator according to claim 16, furthercomprising high-temperature refrigerant piping provided between one ofsaid vacuum heat insulators and said outer box.
 18. The refrigeratoraccording to claim 16, wherein said at least one vacuum heat insulatorincludes a vacuum heat insulator that is provided between said machineroom and said freezer compartment.
 19. The refrigerator according toclaim 13, further comprising independent compartments having differenttemperature ranges, and an evaporator for each of said compartments,wherein said at least one vacuum heat insulator includes a vacuum heatinsulator that is disposed in a heat insulating portion behind at leastone of said evaporators.
 20. The refrigerator according to claim 19,wherein said at least one vacuum heat insulator includes a vacuum heatinsulator that is disposed in a partition between said independentcompartments.
 21. The refrigerator according to claim 13, furthercomprising a compressor, wherein said at least one heat insulatorincludes a vacuum heat insulator that is disposed in a partition betweensaid compressor and said inner box.
 22. The refrigerator according toclaim 13, further comprising a control circuit board, wherein said atleast one vacuum heat insulator includes a vacuum heat insulator that isdisposed in a partition between said control circuit board and saidinner box.
 23. The refrigerator according to claim 13, furthercomprising a condenser in a bottom thereof, wherein said at least onevacuum heat insulator includes a vacuum heat insulator that is disposedin a partition between said condenser and said inner box.
 24. Therefrigerator according to claim 13, further comprising a thermoplasticresin layer on at least a portion of an inner surface partially definingsaid space between said outer box and said inner box, wherein at leastone of said plural vacuum heat insulators is adhered to said innersurface via said thermoplastic resin layer by performing a hot meltbonding operation.